Solar battery module and method for manufacturing the same

ABSTRACT

Provided is a solar battery module wherein solar battery cells are electrically connected to each other by using a wiring board having a predetermined wiring pattern formed on a resin base material. A method for manufacturing such solar battery module is also provided. In the wiring board of the solar battery module, a direction wherein a design margin is small is permitted to be a direction wherein the thermal contraction ratio of the resin base material is small, by the shape of an electrode pattern on the solar battery cell and that of the wiring pattern on the wiring board. At the time of manufacturing such solar battery module, temperature in a heat treatment step is set at 100° C. or higher but not higher than 180° C. Electrode designing at a fine pitch is made possible and the solar battery module exhibits high solar battery characteristics, even when the solar battery cells are connected by using wiring boards composed of various types of resin materials having thermal compression ratio not sufficiently low.

RELATED APPLICATIONS

The instant application is a divisional application of co-pending U.S.patent application Ser. No. 13/002,116, filed Dec. 30, 2010, which isthe U.S. national phase of International Application No.PCT/JP2009/062038, filed Jul. 1, 2009, which designated the U.S. andclaims priority to JP Application No. 2008-173045, filed Jul. 2, 2008,the entire contents of each of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a solar battery module and a method formanufacturing the same that are able to use a wiring board which isformed of various resin materials.

BACKGROUND ART

In recent years, because of global environmental problems such asdepletion of energy sources, increase in carbon dioxide in theatmosphere and the like, a clean energy source is desired to bedeveloped, especially, photovoltaic power generation that uses solarbattery cells is developed as a new energy source, put into practicaluse and is on the way of development. As for the solar battery cell,conventionally, the mainstream is a solar battery module that has astructure in which on a light receiving surface of a monocrystalline orpolycrystalline-electroconductive-type silicon substrate, a pn junctionis formed by diffusing reverse electroconductive-type impurities; and aplurality of solar battery cells, in each of which electrodes are formedon the light receiving surface and a back surface of the siliconsubstrate, are connected to each other.

Besides, another solar battery cell is also widespread, in which animpurity layer that contains the same electroconductive impurities at ahigh density is formed on a back surface of one electroconductivity typesilicon substrate, so that a high output due to a back-surface fieldeffect is obtained. Moreover, a so-called back electrode-type solarbattery cell is also developed, in which an electrode is not formed on alight receiving surface of a silicon substrate; instead, a P electrodeand an N electrode are formed on a back surface of the siliconsubstrate.

Because the back electrode-type solar battery cell generally does nothave an electrode on the light receiving surface, so that it is expectedto obtain a high output compared with a solar battery cell that has anelectrode on each of the light receiving surface and the back surface ofthe silicon substrate.

Because of this, a proposition is provided, in which the backelectrode-type solar battery cells are connected to each other by meansof a wiring board in which wirings are formed on an insulating base, sothat the connection of the back electrode-type solar battery cellsbecomes easy and it is possible to reduce cell flaws (e.g., see patentdocument 1).

PRIOR-ART DOCUMENT Patent Document

Patent document 1: JP-A-2005-340362

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

A proposition to use a wiring board is provided to ease connection ofsolar battery cells, which, however, does not lead to mass-production.As a wiring board that is used in the field of semiconductors, there area hard board in which a wiring pattern is formed of copper film and thelike on a glass-epoxy base plate that has small thermal shrinkage; and aflexible board in which a wiring pattern is formed of copper film andthe like on a polyimide film. However, the glass-epoxy base plate andthe polyimide film used for these wiring boards are very expensivebecause they require 1 m² or more per unit as a material for a solarbattery cell module, which is a major cause of the fact that themass-production is not performed.

To avoid this, there is an idea to use an inexpensive material; however,an inexpensive material generally has a problem with thermal stability.As for a procedure of manufacturing a solar battery module, a wiringboard is heated in a process of connecting the solar batter cells andthe wiring board to each other or in a process of sealing the solarbattery module by means of a weather-proof seal material, so that thewiring board is likely to be exposed to a temperature of about 150° C.

For example, in a case where instead of a polyimide film, a PET film,which has a price that is one in several tens times the price of thepolyimide film, is used, in comparison of the films themselves with eachother, a dimensional change of the polyimide film is 0.1% or smallerunder heat treatment at 150° C. and for 30 minutes, while the PET filmsometimes shrink by several percent; a dislocation occurs between theelectrode of the solar battery cell and the wiring of the wiring board,which is highly likely to lead to a defective module.

Generally, if the electrodes of a back electrode-type solar battery cellare dense and have a fine pitch, a high solar battery characteristic isexpectable; however, in light of the thermal shrinkage of the film, itis hard to design electrodes that are dense and have a fine pitch, whichraises a problem that it is impossible to show a high solar batterycharacteristic.

Because of this, in light of the above problems, it is an object of thepresent invention is to provide a solar battery module and a method formanufacturing the same that allow electrode designing at a fine pitchand show a high solar battery characteristic even in a structure inwhich the solar battery cells are connected by means of a wiring boardthat is formed of various resin materials whose thermal shrinkages arenot sufficiently low.

Means for Solving the Problem

As a result of a hard study to achieve the above object, as for a resinfilm which is generally manufactured by a biaxial stretch method, whenmanufacturing the resin film by winding it into a roll shape, adifference in thermal shrinkage ranging from several times to severaltens times occurs between an MD direction (winding direction) and a TDdirection (direction perpendicular to the MD); for example, as for ageneral inexpensive PET film, under heat treatment at 150° C. and for 30minutes, there is about 2% thermal shrinkage in the MD direction andabout 0.2% thermal shrinkage in the TD direction; in light of this, itis possible to manufacture a wiring board that is subjected to onlysufficiently small influence of the thermal shrinkage by using adirection that has a fine electrode pattern and a small design margin asthe TD direction, the inventor became aware of which and came to thepresent invention. In other words, the present invention relates a solarbattery module that electrically connects solar battery cells to eachother by means of a wiring board in which a predetermined wiring patternis formed on a resin base, wherein in the wiring board, based on shapesof the electrode pattern of the solar battery cell and of the wiringpattern of the wiring board, the direction that has a small designmargin is used as a direction in which the thermal shrinkage of theresin base is small.

According to this structure, by matching the direction in which thethermal shrinkage of the resin base is small with the direction whichhas a small design margin and needs to curb an error small, it ispossible to obtain a wiring pattern in which the influence of thethermal shrinkage is curbed. Because of this, it is possible to obtain asolar battery module that includes a wiring board that is formed bymeans of various resin materials whose thermal shrinkages are notsufficiently low.

Besides, in the solar battery module having the above structureaccording to the present invention, a width direction of the wiringpattern in which a plurality of wirings are disposed adjacent to and inparallel with each other is used as the TD direction of the resin base.According to this structure, in the wiring pattern for connecting thesolar battery cells that have repeated patterns which are relativelysimple and the same as each other, the width direction in which thewiring is performed at a fine pitch is employed as the TD direction ofthe resin base; and the direction in which a large pattern margin issecured is employed as the MD direction, so that it is possible toobtain a wiring pattern that is not subjected to the influence of thethermal shrinkage.

Besides, in the solar battery module having the above structureaccording to the present invention, the resin base is a biaxiallystretched resin film. According to this structure, it is possible toselect and use a resin suitable for the wiring board from many resinmaterials that are generally manufactured by the biaxial stretch method.

Besides, in the solar battery module having the above structureaccording to the present invention, the film is a polyester-relativefilm. According to this structure, it is possible to manufacture thewiring board of the solar battery module by means of a resin materialthat is inexpensive and mass-producible.

Besides, in the solar battery module having the above structureaccording to the present invention, the film contains either ofpolyethylene terephtalate (PET) and polyethylene naphtalate (PEN).According to this structure, even by means of a resin material that haslarge thermal shrinkage and is very inexpensive, by using the widthdirection as the TD direction, it is possible to manufacture the wiringboard that is subjected to only sufficiently small influence of thethermal shrinkage.

Besides, the present invention relates to a method for manufacturing thesolar battery module according to any one of claims 1 to 5, wherein atemperature in a heat treatment step is kept from 100° C. or higher to180° C. or lower.

According to this structure, even when the heat treatment is performedfor adhesion, electrode connection and the like, by keeping the heattemperature at 180° C. or lower, it is possible to prevent a positionaldislocation due to the thermal shrinkage even when an inexpensive resinmaterial having a low thermal-stability temperature is used.

Besides, in the method for manufacturing the solar battery module havingthe above structure according to the present invention, a solder thathas a melting point of 180° C. or lower or an electroconductive adhesivethat hardens at a temperature of 180° C. or lower is used for theconnection between the electrode of the solar battery cell and thewiring board. According to this structure, while curbing the thermalshrinkage of the resin base under the heat treatment temperature of 180°C. or lower, it is possible to surely perform the connection between theelectrode of the solar battery cell and the wiring board.

Advantages of the Invention

According to the present invention, in a solar battery module thatelectrically connects solar battery cells to each other by means of awiring board in which a predetermined wiring pattern is formed on aresin base, as for the wiring board, based on shapes of an electrodepattern of the solar battery cell and of the wiring pattern of thewiring board, a direction that has a small design margin is used as adirection in which thermal shrinkage of the resin base is small, thedirection in which the thermal shrinkage of the resin base is small ismatched with a direction which has a small design margin and needs tocurb an error small, so that it is possible to obtain a wiring patternwhich curbs the influence of the thermal shrinkage. Because of this, itis possible to obtain the solar batter module that includes the wiringboard that is formed of various resin materials whose thermal shrinkagesare not sufficiently low. Besides, by using a method for manufacturingthe solar battery module in which a temperature in a heat treatment stepis kept from 100° C. or higher to 180° C. or lower, it is possible tomanufacture the solar battery module that includes the wiring boardwhich prevents a positional dislocation caused by the thermal shrinkageeven when various inexpensive resin materials having lowthermal-stability temperatures are used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (a) shows a sectional schematic view of a solar cell battery;FIG. 1 (b) is a plan view showing a solar battery cell on which alinear-shape electrode pattern is formed; FIG. 1 (c) is a plan viewshowing a solar battery cell on which a dot-shape electrode pattern isformed; and FIG. 1 (d) is a plan view showing a solar battery cell onwhich a comb-teeth-shape electrode pattern is formed.

FIG. 2 is a plan view showing an example of a wiring board.

FIG. 3 (a) is a sectional schematic view of a first embodiment of asolar battery cell; and FIG. 3 (b) is a plan view of a first embodimentof a solar battery cell.

FIG. 4 is a plan view showing another example of a wiring board.

FIG. 5 (a) is a plan view of an example solar battery module; and FIG. 5(b) is a sectional schematic view of an example solar battery module.

FIG. 6 is a sectional view showing an important structure in asemi-finished state before a frame body and a terminal box of a solarbattery module according to the present invention are mounted.

FIG. 7 is a sectional view showing an important structure in a finishedstate of a solar battery module according to the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention are described withreference to the drawings. Besides, the same constituent members areindicated by the same reference numbers and detailed description issuitably skipped.

A solar battery module includes: a solar-battery main body portion thathas a plurality of solar battery cells; a frame body that holds acircumference of the solar-battery main body portion into a unitarybody; a terminal box that serves as an output portion for electric powergenerated by the solar-battery main portion; and an output cableconnected to the terminal box; wherein the solar battery module has astructure in which in order from the surface, a light-receiving surfaceprotection plate that is formed of light-transmissive glass or of aplastic material; a solar-battery cell seal member that is formed of asheet-shape ethylene vinyl acetate and the like; a solar battery cellthat is formed of monocrystalline silicon, polycrystalline silicon, achemical semiconductor or the like which is sealed in the solar-batterycell seal member; and a back-film laminated body that protects thesolar-battery cell seal member from a back surface are unitarily formedand built in the frame body.

The solar battery module has a structure in which the plurality of solarbattery cells, in each of which a string is electrically wired by meansof an inter-connector and an electrode is formed on a glass base plate,are set in series/in parallel with each other; placed between thelight-receiving surface protection plate and the back film on the backsurface; sealed by means of a light-transmissive resin; and the framebody is mounted on the circumference. The solar battery cell in thepresent embodiment is a back-electrode solar battery cell 10 in whichboth of an N electrode and a P electrode are formed on the back surfaceand which has, for example, a structure shown in a sectional schematicview of FIG. 1 (a) which is so structured as to include: a siliconsubstrate 1; a reflection protective film 2 that is formed on a lightreceiving surface of the silicon substrate 1; an N+ layer 3 and a P+layer 4 that are formed on a back surface of the silicon substrate 1; apassivation film 7, an N electrode 5, and a P electrode 6 that areformed on the back surface. Besides, a structure may be employed, inwhich another passivation film is formed between the silicon substrate 1and the reflection protective film 2.

It is possible to form the reflection protective film 2 and thepassivation film 7 of, for example, a silicon nitride film or a siliconoxide film.

It is possible to form an electrode pattern disposed on the back surfaceinto: a linear-shape electrode pattern as shown in FIG. 1 (b); adot-shape electrode pattern as shown FIG. 1 (c); and a comb-teeth-shapeelectrode pattern as shown FIG. 1 (d); thus, a solar battery cell 10A isformed, on which the linear-shape electrode pattern including an Nelectrode 5 a and a P electrode 6 a that are formed into the linearshape is formed; a solar battery cell 10B is formed, on which thedot-shape electrode pattern including an N electrode Sb and a Pelectrode 6 b that are formed into the dot shape is formed; and a solarbattery cell 10C is formed, on which the comb-teeth-shape electrodepattern including an N electrode 5 c and a P electrode 6 c which areformed into the comb-teeth shape is formed. Next, a wiring board, whichis mounted to connect the plurality of electrodes of the plurality ofsolar battery cells 10 (10A, 10B, 10C) and to draw out an electromotiveforce, is described.

Wiring boards are things in each of which a desired wiring pattern isformed on an insulating base plate; and include wiring boards that use ahard base plate as the insulating base plate and wiring boards that usea film base plate as the insulating base plate. The present embodimentemploys a wiring board that uses a film manufactured by the biaxialstretch method.

As for the wiring board, an insulating film that serves as a base andmetal foil, for example, are attached to each other by means of anadhesive and the like; a protective resist is formed into a desiredshape on a surface of the metal foil; thereafter, etching is applied toexposed metal foil to remove the resist, so that the wiring board havinga desired wiring pattern is formed. At this time, a direction of thefilm is decided in accordance with the formed wiring pattern, so that itis possible to manufacture the wiring board that is highly resistant tothermal shrinkage.

Generally, the manufacture of a film is performed by means of thebiaxial stretch method, in which a dissolved resin base is wound into aroll shape, while it is stretched in a longitudinal direction (windingdirection: MD direction) and in a transverse direction (TD direction:direction perpendicular to the MD direction), so that aconstant-thickness film is manufactured. The method has a feature that astress is likely to remain in the MD direction; accordingly, whenthermal shrinkage occurs, the shrinkage is likely to occur in the MDdirection: sometimes, the thermal shrinkage that is a few times toseveral tens times larger than the shrinkage in the TD direction occurs.In other words, the thermal shrinkage of the resin base in the TDdirection becomes small, while the thermal shrinkage in the MD directionbecomes large.

Because of this, as a resin base of a flexible wiring board that is usedin the field of semiconductors, a polyimide film, which is excellent inthermal stability and whose shape change hardly occurs even when heatedto two hundred and several tens degrees Celsius, is used. However, thepolyimide film is very expensive, and in a case where it is used as awiring board for a solar battery module, in light of the fact that anarea equal to the module area is required, it is hard to perform themass-production.

On the other hand, polyester-relative films such as PET (polyethyleneterephtalate), PEN (polyethylene nahtalate) and the like are widespreadfor general uses as a packaging material and inexpensive, that is, somefilms have a price which is one in several tens times the price of thepolyimide film. However, the polyester-relative film is considerablyinferior to the polyimide film in thermal stability; although there is acase where the polyester-relative film is used as a base for a wiringboard, the polyester-relative film is limited to uses in which it is notsubjected to heat. For example, it is known that under heat treatment at150° C. and for 30 minutes, a general PET film itself shows 2% thermalshrinkage in the MD direction and 0.2% thermal shrinkage in the TDdirection. Actually, because metal foil is attached, the thermalshrinkage becomes smaller than the foregoing values; however, it is truethat the shrinkage in the MD direction is larger than that in the TDdirection. Besides, the specific shrinkage changes from wiring patternto wiring pattern.

In a case where a wiring board is used in a solar battery module, duringa time of manufacturing the module, heating at at least 100° C. orhigher is required in both steps for connection to the solar batterycell and for sealing the solar battery module. Besides, as for a generalPET resin, because a color change, a property change, and a deformationoccur, it is necessary to keep the treatment temperature at 180° C. orlower. The same thing is also true of the PEN and otherpolyester-relative films although there is a sort of difference. Becauseof this, in a use in which a wiring board is used in a solar batterymodule, in the interest of thermal shrinkage, generally, in the field ofsemiconductors, the polyester-relative film is not used as the base ofthe wiring board. However, in a solar battery cell, unlike asemiconductor, it is not necessary to use a wiring pattern that is denseand complicated in both of a longitudinal direction and a transversedirection: a simple pattern that is described later is used, in which adirection that requires a high accuracy is limited to one direction;accordingly, the pattern is formed in such a way that the directionwhich requires the high accuracy is used as the TD direction of theresin base, while the other is used as the MD direction, so that itbecomes possible to be use the polyester-relative film. According tothis, it is possible to use the inexpensive polyester film for thewiring board; and as a result of this, it becomes possible tomass-produce the solar battery module.

FIG. 2 shows an example of the wiring board. This wiring board is awiring board 20 (it is possible to dispose even an comb-teeth-shapeelectrode on this wiring board) that is formed with a comb-teeth-shape Pwiring and an N wiring faced with each other; the comb-teeth-shape Pwiring and N wiring are so formed as to correspond to the electrodesdisposed on the solar battery cell 10A on which the linear-shapeelectrode pattern is formed or on the solar battery cell 10B on whichthe dot-shape electrode pattern is formed; in a case where a pluralityof (e.g., 12) solar battery cells are disposed, connection wirings 9 ato 9 m for connecting the plurality of solar battery cells in series areprovided. It is desirable that the wiring (P wiring and N wiring) thatis formed corresponding to the electrode formed on the solar batterycell has a width equal to or wider than the electrode width; byconnecting the electrode of the solar battery cell and the wiring of thewiring board to each other in such a way that they overlap each other,the wiring for the solar battery module is performed. As describedabove, by laying the electrode and the wiring on each other, it ispossible to lower electric resistance in collecting electricity that isgenerated by the solar battery cell, so that a high solar batterycharacteristic is obtained.

Here, to connect the wiring of the wiring board and the solar batterycell to each other, by means of, for example, a solder that has a lowmelting point and a low-temperature hardening type electrocoductiveadhesive, the heat temperature for the connection is kept at 180° C. orlower. In this case, if the polyester-relative film such as the PET, PENor the like is used for the resin base of the wiring board, even at atreatment temperature that is a relatively low temperature which is 180°C. or lower, a positional dislocation due to the thermal shrinkageoccurs, which is likely to lead to defective wiring. Accordingly, it ishighly likely that one electrode of the solar battery cell and thewiring that connects to the other adjacent electrode come into contactwith each other; because of this, a wiring board formed of a resin baseis used, in which an X direction in which many wirings are so formed asto be adjacent to each other matches the TD direction of the resin baseand a Y direction matches the MD direction.

As described above, by means of the wiring board 20 in which the widthdirection of the wiring pattern, in which the plurality of wirings aredisposed adjacent to and in parallel with each other, is used as the TDdirection of the resin base, the width direction in which the wiring isperformed at a fine pitch is used as the TD direction of the resin base,and the direction which allows a large pattern margin to be secured isused as the MD direction of the resin base, so that it is possible toachieve a wiring pattern which is prevented from being dislocated by thethermal shrinkage and is not subjected to the influence of the thermalshrinkage.

Next, a type of solar battery cell, in which electricity is collectedinto a bus-bar electrode that is formed on a cell end portion via acomb-teeth-shape finger electrode of the solar battery cell, and a solarbattery module including a wiring board which performs connection via aconnection wiring that comes into contact with the bus-bar electrode aredescribed with reference to FIG. 3 and FIG. 4.

The solar battery cell 10C shown in FIG. 3 (a) is a back-electrode typesolar battery in which both of the N electrode 5 and the P electrode 6are formed on the back surface; and is so structured as to include: forexample, an N-type silicon substrate 1; a reflection protective film 2that is formed on a light receiving surface of the silicon substrate 1;an N+ layer 3 and a P+ layer 4 that are formed on the back surface ofthe silicon substrate 1; and a passivation film 7, the N electrode 5,and the P electrode 6 that are formed on the back surface. Besides, asshown in FIG. 3 (b), the N electrode 5 formed on the solar battery cell10C in the present embodiment is a finger N electrode 5 c; and the Pelectrode 6 is a finger P electrode 6 c; these are formed into acomb-teeth shape; a bus-bar N electrode 50 and a bus-bar P electrode 60are formed on the cell end portion.

An example of a wiring board 21 that is used corresponding to the abovesolar battery cell 10C is shown in FIG. 4. The wiring of the wiringboard used here has: a wiring pattern that connects, in series, thebus-bar N electrode 50 and the bus-bar P electrode 60 which are adjacentto each other; and the connection wirings 9 (9 a to 9 m) that forms awiring pattern that connects solar battery strings to each other.

By connecting the bus-bar electrodes (bus-bar N electrode 50, bus-bar Pelectrode 60) of the solar battery cell to the connection wirings 9 (9 ato 9 m), the wiring for the solar battery module is performed. In otherwords, electric currents are captured by only the finger electrode ofthe solar battery cell and collected into the bus-bar electrodes formedon the cell end portion. As described above, it is sufficient to performthe wiring by laying only the bus-bar portion on the connection wiring 9of the wiring board, it is easy to perform positioning for thedisposition although an idea is required to lower the resistance of thefinger electrode in such a way that a loss does not occur in the fingerelectrode.

In this case, as for the connection between the bus-bar electrode andthe connection wiring, by means of the above solder having a low meltingpoint and the low-temperature hardening type electroconductive adhesive,it is possible to keep the heat temperature for the connection at 180°C. or lower. Besides, in this case, if the base of the wiring board is apolyester-relative film such as PET, PEN or the like, even under thetreatment at 180° C. or lower, a positional dislocation due to thethermal shrinkage is likely to occur and lead to defective wiring;accordingly, it is desirable to use the wiring board 21 which as the TDdirection of the resin base, uses the Y direction in the figure that ishighly likely to come into contact with an end portion of the fingerelectrode.

As described above, by means of the wiring board 21 which as the TDdirection of the resin base, uses the direction that is highly likely tocome into contact with another electrode and has a small design margin,it is possible to achieve the wiring board which is prevented from beingdislocated by the thermal shrinkage and is not subjected to theinfluence of the thermal shrinkage.

After the wiring board 21 is mounted and connected, the solar batterycells 10C and the wiring board 21 are sandwiched by means of alight-transmissive seal member such as EVA (ethylene•vinyl•acetate) orthe like, a light-transmissive base plate such as glass, and aweather-proof film; heat vacuum press bonding and annealing areperformed; the module is sealed; the frame body and a terminal box fordrawing out electricity to outside are mounted, so that the solarbattery module is completed.

As described above, based on the shapes of the electrode pattern of thesolar battery cell and of the wiring pattern of the wiring board, thedirection that has a small design margin is used as the direction inwhich the thermal shrinkage of the resin base is small; the direction inwhich the thermal shrinkage of the resin base is small is matched withthe direction which has a small design margin and needs to curb an errorsmall, so that it is possible to obtain the wiring pattern which curbsthe influence of the thermal shrinkage; and to obtain the solar batterymodule that includes the wiring board which is formed of various resinmaterials whose thermal shrinkages are not sufficiently low.

Even in the steps of the heat vacuum press bonding and the annealing,depending on the kind of the seal member used, generally, the heating isperformed at 120 to 180° C. for about 10 to 60 minutes; accordingly, ifa polyester-relative film is used for the wiring board, a positionaldislocation between the solar battery cell and the wiring board islikely to occur because of the thermal shrinkage. Even in this case, byusing the direction that has a small design margin as the TD directionof the resin base, it is possible to prevent a defect from occurring inthe module caused by a positional dislocation.

As described above, the wiring pattern used in the solar battery moduleis simple and has the same pattern for all the cells; accordingly, thedirection that has a small design margin is used as the TD direction ofthe base film, and the direction has a margin is used as the MDdirection, so that it becomes possible to use polyester-relative filmssuch as PET, PEN and the like that are very inexpensive but have largethermal shrinkage.

Examples

As examples, a solar battery module M is fabricated by means of: thesolar battery cell 10A on which the linear-shape electrode pattern shownin FIG. 1 is formed; and the wiring board 20 shown in FIG. 2. As for thesolar battery cell 10A, as shown in FIG. 1 (a), the N+ layer 3 and theP+ layer 4 are alternately formed on the back surface of the solarbattery; the reflection protective film 2 including, for example, anitride silicon film is formed on the light receiving surface, and thepassivation film 7 is formed on the back surface; the N electrode 5 andthe P electrode 6 are formed on the N+ layer and the P+ layer,respectively. It is possible to fabricate the solar battery cell 10Ahaving this structure by means of a known method. Here, the solarbattery cell 10A is a baked electrode that contains silver as a maincomponent; the linear-shape N electrode 5 a and the P electrode 6 a arealternately formed, and the distance between the N electrode 5 a and theP electrode 6 a is set at 0.5 mm. Besides, the widths of both electrodesare set at 0.2 mm. Besides, a solder (Sn—Bi solder) H is applied to thesurface of the electrode.

Next, as for the wiring board 20, a PET film 25 μm thick is used for thebase and is attached to copper foil 35 μm thick by means of an adhesive;thereafter, a protective resist is formed and etching is performed toobtain a desired shape, so that the wiring board 20 is fabricated. Onthe wiring board 20, the comb-teeth-shape N wiring and P wiring areprovided; and a connection wiring, which connects an N-type wiringelectrically connected to an N-type electrode of the back-electrode typesolar battery cell with a P-type wiring electrically connected to aP-type electrode of the solar battery cell adjacent to the N-typeelectrode, is formed. Besides, a wiring by which strings are connectedin series with each other is also formed.

Here, the width of the wiring at the portion that overlaps the electrodeof the solar battery cell is set at 0.35 mm. The reason the width of thewiring is wider than the width 0.2 mm of the above electrode is toprevent the cell characteristic from being deteriorated by electricresistance in collecting electric currents generated by the solarbattery cells; and the distance from the electrode having an oppositepolarity and being adjacent to the wiring is 0.15 mm. Besides, thedistance between the places of the comb-teeth-shape N wiring, P wiringwhere the bus-bar electrodes are formed and the tip end of the solarbattery cell having an opposite polarity is set at 0.5 mm. Besides, thewiring board is fabricated with the X direction of the module having thesmall design margin used as the TD direction of the base.

Next, as shown FIG. 5 (a), a total of 12 solar battery cells 10A (10 ato 101) are placed on the wiring board and temporarily fixed by means ofa UV hardening adhesive in such a way that the solar battery cell is notdislocated. And, as shown FIG. 5 (b), the N electrode 5 a and the Nwiring 91 are electrically connected to each other by reflow soldering,and the P electrode 6 a and the P wiring 92 are electrically connectedto each other by reflow soldering. This reflow soldering is a solderingmethod in which the solder H is applied to a point to be connected inadvance; an electronic component is placed on the point; and heating isperformed; in the present embodiment, the peak temperature of theheating is set at 150° C.

Next, as shown in FIG. 6, an EVA film as the seal member is disposed onthe light receiving surface and on the back surface; moreover, a glassbase plate 11 is disposed on the light receiving surface, and aweather-proof film 12 is disposed on the back surface; the heat vacuumpress bonding is performed by means of a laminator; moreover, theannealing is performed, and the solar battery module is sealed. As forthe heat temperature and the treatment time in each step are: 130° C.and for 5 minutes in the laminator, while 140° C. and for 40 minutes inthe annealing.

Via the above steps, as shown in FIG. 7, an aluminum frame body 30 isdisposed around the module; a terminal box 8 for drawing out electricityto outside is mounted, so that 2 solar battery modules M (MA and MB) arecompleted. It is possible to draw out electricity generated by the solarbattery module M via an output cable 81.

Comparison Examples

As comparison examples, the TD direction of the PET film that is thebase of the wiring board is set to the Y direction, and the MD directionis set to the X direction of the board shape, that is, changed-overdirections; and the other conditions are the same as those for theexamples; thus, 2 solar battery modules Ma, Mb are fabricated.

Tests of checking for occurrence of defective modes and for the numberof defective cells are performed for the solar battery modules MA, MBthat are fabricated as the examples and the solar battery modules Ma, Mbthat are fabricated as the comparison examples. The results are shown intable 1.

TABLE 1 Good/Poor Module Determination Defective Mode Defective CellComparison Poor Short-circuit 2 example Ma occurred Comparison PoorShort-circuit 2 example Mb occurred Example MA Good Zero Zero Example MBGood Zero Zero

The cause of the defects that occur in the comparison examples is that 2of 12 solar battery cells are short-circuited because of a positionaldislocation in both of the comparison examples Ma, Mb. The 2 examplesMA, MB are fabricated with no problem; and defects due to a positionaldislocation do not occur at all: it is confirmed that by using thedirection which does not have a dimensional margin and has a smalldesign margin as the TD direction of the base film, the examples becomeunlikely to be subjected to the influence of the thermal shrinkage.

As described above, as for the resin base of the wiring board, based onthe shapes of the electrode pattern of the solar battery cell and of thewiring pattern of the wiring board, the direction that has a smalldesign margin is used as the direction in which the thermal shrinkage ofthe resin base is small, while the width direction in which theplurality of wirings of the wiring pattern are disposed in parallel witheach other is used as the TD direction of the resin base; thus, in thewiring pattern for connecting the solar battery cells that have repeatedpatterns which are relatively simple and the same as each other, thewidth direction in which the wiring is performed at the fine pitch isused as the TD direction of the resin base; and the direction in whichthe large pattern margin is secured is used as the MD direction, so thatit is possible to obtain the wiring pattern that is not subjected to theinfluence of the thermal shrinkage.

Because of this, even if the solar battery module according to thepresent invention has a structure in which the solar battery cells areconnected by means of a wiring board that is formed of various resinmaterials whose thermal shrinkages are not sufficiently low, the solarbattery module allows the electrode design at a fine pitch and shows ahigh solar battery characteristic.

Besides, as for the method according to the present invention formanufacturing a solar battery module, the solar battery module havingthe above structure is manufactured at the heat-treatment temperature of100° C. or higher to 180° C. or lower, so that even if a resin materialthat has a low thermal-stability temperature and inexpensive is used,the manufacturing method is able to prevent a positional dislocationcaused by thermal shrinkage and does not manufacturer a defectiveproduct.

Because of this, according to the present invention, in a solar batterymodule that connects solar batter cells to each other by means of awiring board in which a predetermined wiring pattern is formed on aresin base, as for the wiring board, based on shapes of an electrodepattern of the solar battery cell and of the wiring pattern of thewiring board, a direction that has a small design margin is used as adirection in which thermal shrinkage of the resin base is small, thedirection in which the thermal shrinkage of the resin base is small ismatched with a direction which has a small design margin and needs tocurb an error small, so that it is possible to obtain a wiring patternwhich curbs the influence of the thermal shrinkage; and to obtain asolar battery module that includes the wiring board which is formed ofvarious resin materials whose thermal shrinkages are not sufficientlylow. Besides, by means of a method for manufacturing the solar batterymodule in which a temperature in a heat treatment step is kept from 100°C. or higher to 180° C. or lower, it is possible to manufacture thesolar battery module that includes the wiring board which prevents apositional dislocation caused by the thermal shrinkage even when aninexpensive resin material having a low thermal-stability temperature isused.

INDUSTRIAL APPLICABILITY

The solar battery module according to the present invention becomes asolar battery module that includes a wiring board that is formed ofvarious resin materials whose thermal shrinkages are not sufficientlylow, so that the solar battery module becomes applicable to the field ofsolar batteries where the mass-production is required.

LIST OF REFERENCE SYMBOLS

-   -   1 silicon substrate    -   2 reflection protective film    -   3 N+ layer    -   4 P+ layer    -   5 N electrode    -   6 P electrode    -   7 passivation film    -   9 connection wiring    -   10 solar battery cell    -   20 wiring board    -   21 wiring board    -   30 frame body    -   H solder    -   M solar battery module

1. A wiring board which is used to electrically connect a backelectrode-type solar battery cell and in which a wiring pattern isdisposed on a resin base, wherein the wiring pattern is disposed in afirst direction and in a second direction which is perpendicular to thefirst direction, either one of the first direction and the seconddirection, which has a smaller pitch in the wiring pattern than another,is a TD direction of the wiring board, and the resin base is a film thatincludes: an MD direction; and the TD direction which is perpendicularto the MD direction and has a thermal shrinkage smaller than a thermalshrinkage in the MD direction.
 2. The wiring board according to claim 1,wherein the resin base is a biaxially stretched resin film.
 3. Thewiring board according to claim 1, wherein the film is apolyester-relative film.
 4. The wiring board according to claim 3,wherein the film contains either of a polyethylene terephtalate and apolyethylene naphtalate.
 5. A solar battery module comprising: thewiring board according to claim 1; and a back electrode-type solarbattery cell.